Synthesis of dialkylamidoamine oxide surfactant and characterization of its dual function of detergency and softness

In this study, an amine oxide surfactant of high molecular weight having a dialkyl amide chain was synthesized mainly for detergent formulation purpose where solubility of a newly synthesized surfactant was controlled by adduct with 5 mol of ethylene oxide and 2 mol of propylene oxide. The characterization of a surfactant was performed by ¹H NMR and ¹³C NMR and the composition was compared with the expected composition calculated from the equilibrium distribution of feeding materials. Since this newly synthesized surfactant is a bulky amphoteric surfactant, it can serve as a dual function surfactant depending on pH variation of the aqueous solution. The new amine oxide surfactant showed not only detergency but also mildness effect since it showed characteristics of a nonionic surfactant in an alkaline condition, while showing characteristics of a cationic surfactant in a neutral pH condition. The dual function characteristics depending on pH of the aqueous solution were investigated using QCM (quartz crystal microbalance) and zeta potential measurement with related cleaning and mildness tests. In addition, the physical properties of an amine oxide surfactant such as critical micelle concentration, surface tension, interfacial tension, contact angle and viscosity were measured.